Uneven Idleing & Engine Stalls

Hey!
Just one quick question for y'all. I have a '94 Talon ESi. At times (rather unsystematically) my idle speed seems to either change and/or go up and down at a constant rate. It is odd due to the fact that it will be working fine at one point and then I shut off my car, come back 5 mins later and it will start doing it. Any suggestions? As well, it seems at times (usually when it is cold, not always though) That my car will start up all good, warm up and when I go to drive away it will stall out when I put the clutch in. And, it will either get going normal, or it will be running good from the start and I will be driving along and when I put the clutch in, it will stally out. Please let me know if you have any ideas as to what is happening. Thanks!

i had the same problem with my car it was the altanator!!!!!!!!

It was the alternator?? That is interesting. That did not even occur to me, but I just got my alternator belts replaced and the alternator tightened up (my story is in some other threads in this forum). So, basically it was the alternator and it needed to be replaced? did they say what was wrong with it, or that it was just worn out. or what? did they say how that would affect the weird reving of the engine and the stalls?

bump :banghead:

Well, I got a fuel injector flush and it seemed to fix my problems. Then, they started again. So, if ANYONE has any idea (other than the alternator) Please let me know. Thanks

Just a thought, I'm barely even a novice here :P. But when the last time you had your fuel filter changed? you said the flush helped the problem, if your fuel filter is partway clogged it will bypass the clogged part and still work, but your gas won't be getting filtered right so it would clog the injecters back up pretty quick.

There is a switch, on top of the throttle body right where the air intake hose connects to it. If you know where the idle control screw is, you should be able to see this switch which hooks up only by a single wire. I believe it is called the idle speed control sensor switch. Mine some how came off and it caused my car to idle unevenly and stall. Maybe yours did or the switch is faulty. Check it because mine did idle correctly sometimes but I haven't had a problem with it since I reconnected that wire.

Actually that's a throttle stop switch (I'm not sure that's the official name for it). Basically it tells the ECM that the throttle is in the idle position. You can check it with an ohmeter or a continuity tester, it is either on or off. I don't remember if you get continuity when the throttle is closed, or if continuity stops when the throttle is closed. It would be simple enough to check though.

caniborrow50cnts, you may be on to something there. If the switch is failing it could be sending an alternating signal to the ecm, i.e., throttle open, throttle closed, etc.. This could actually cause the idle to be inconsistent. I would thing it would be that way all the time though, whether the engine is cold or warm, but it could be making better contact after the engine warms up.

It certainly is worth checking!

Mark

Alright, I will check that. But please, give me some detail as to exactly where the switch is, I know where the idel control screw is, so please tell me where to go from there. Thanks a lot for your help! I really hope that this will work.

Alex

Pictoral?
http://members.shaw.ca/dsm.1000q/Engineprimer/idleswitch.htm

Taloness:
Nice link!

bighauns;
If it helps, that switch has a small plunger on the end, and the plunger comes in direct contact with a tab on the throttle plate bellcrank.

The link taloness provided explains it pretty well. The ECM will only attempt to control the idle when that switch tells it that the throttle plate is in the idle position. Your idle is actually controlled by a small motor that rotaties in one direction or the other, which in turns moves a positioner(there is probably a technical name for it) up or down, which allows more or less air through the throttle body.

Mark

Thank you so much for that link! that whole site is amazing!!! It seems as though I will be able to see what vertyhing does and all that junk. Thanks for all your help and I will see if this remedies the problem

Alright. I tested the continuity of that switch and the first time it was all the way to the right (zero resistance) then, about 30 seconds later i tested it again, and it was at about only half, which seems to me as if it is only at "half idel". I dont know if that switch was disconnected or not or what, but i conencted it and it seemed to drive fine for a while. Then just this morning, it did the crazy rev thing again, but only for a very short while, like maybe 2-5 mins. Do you guys have any idea what is going on? oh yeah, i tried driving with the switch off (even though that site told me not to, haha) and it seemed to drive fine, but it was also driving fine b4 I took it off. so please, let me know what you think, whether it is a bad connection, something other than the plug, or what.

Thanks!
Alex

that seems to be your problem. both of my cars had problems like that and it seemed to be that switch both times

bighauns;
I took a look at my manual last night regarding that switch.

It's proper description is "closed throttle position switch". You should get full continuity on it (zero resistance) when the throttle is closed. You should have no continuity when the throttle is open. If you are intermittently getting resistance on it with the throttle closed (as you described) then you should replace the switch.

If you disconnect the switch, the ECM will never know when the throttle is closed. Therefore, it will never attempt to control the idle. If your idle is set high enough, this may not be a problem for you. However, if you use your A/C, you will have to bump the idle up quite a bit to keep the car from stalling when then A/C cycles on and off. Also, you may run into low idle problems at times when you are using a lot of accessories, for example, a dark snowy day when you might have your wipers, headlights, heater fan, and rear defroster all going at once.

Having the switch disconnected will also end up causing a fault code (14) to be stored in the ECM.

Mark

Alright. I was readin on that site that taloness sent me. I noticed after a while that if I adjust the idel screw thing that I am supposed to ground a connecter by the cruis control box, I am not sure where this is, but it said that if I do not ground it when adjusting the idel then it will cause it to try and adjust itself. I think this is what I ahve done. I have not looked for the white connector as of yet, but if you ahve any idea with what it is please let me know. I feel that this may have something to do with it, and I will also look into replacing the switch. Anyways, let me know on that connector.

Alex

The connector by the cruise control is called an ignition test connector. It isn't actually necessary to ground this, and I say that because you don't want to just arbitrarily ground a connector on the firewall if you aren't sure you have the right one. It doesn't effect the idle that much either, it will lower it about 50 rpms when grounded, that's it. It isn't actually controlling the idle when you ground it, it is causing the ignition timing to change because the ECM stops controlling it when the test lead is grounded.

You don't need to be perfect on your idle adjustment, just close, it isn't critical at all. The quickest way to do it is to disconnect the connector on the closed throttle position switch, then adjust the speed to 700 rpm. That's all there is to it.

Mark

Alright, so what you are saying is to....

disconnect that plug that we esablished the other day, then set my idel with the screw down to 750ish, then plug that thing back in and it will all be good? The reason I ask is because today it started doing the rev thing and then I decided to pull over, I tried unplugging that switch thing and the crazy revs stopped, but then my car ideled somewhat high. So, please tell me what to do. It has been suggested to me that it may be my vacuum lines, is this a possiblity? But please, answer my question about the plug and stuff first.
Thanks Again!
Alex

bighauns;
I have to apologize, I mis-read your earlier post a little bit regarding the white connector. The ignition test connector actually has a sort of white opaque look inside of the terminal, and I thought that's what you might be talking about.

The actual text book way to adjust the idle is to ground the ignition test terminal, which is on the firewall on the passenger side, plus you ground terminal 10 on the diagnostic connector, which is right next to your fuse box under the far left hand side of your dashboard. Terminal 10 is the 3rd terminal down from the top on the left hand side.

Again, I don't advise arbitrarily grounding terminals on the firewall, there are several of them there, unless you are sure you have the ignition test terminal. One of the terminals on the firewall, right next to the battery, is actually a fuel pump test, and you definitely would not want to ground that.

Bottom line is though, as I said in my earlier post, you can take a short cut by disconnecting the closed throttle position switch connector to prevent the ecm from controlling the idle. Adjusting it to 700 RPM this way will put you into factory spec.

However, you mention now that your idle was higher than normal when you disconnected the closed throttle position switch? You may have discovered your problem right there. I mentioned earlier that you have an idle speed control motor, which controls your idle by turning in one direction or the other, which moves a positioner (of sorts) in and out to allow more or less air through the throttle body. I think what's happening is that you have carbon and such built up inside of this mechanism, and it is causing it to stick. This would explain the high idle, and would explain the erratic idle as well. The problem would be more noticable when the engine is cold because that's when the ECM and ISCM are most likely to be controlling the idle.

You can pull the ISCM motor out and clean it, but you really need to pull the throttle body to do that. It's not that hard, except for the fact that you need to disconnect two hoses that plug into it from the cooling system.

Mark

bighauns;
One more thing, this probably goes without saying, but to be sure; it would be pointless to try and adjust the idle if your ISC is sticking. You need to get it cleaned up and working properly first.

Mark

Alright. I think I understand what you are saying, but please just go over exactly what I should do to get this idealing properly and smoothly. Please let me know exactly what to ground and where and all that fun stuff. Thanks so much for your help, I am glad we almost got this all done!! :-)

Alex

Bighauns;
Sorry I couldn't respond sooner, it was a busy weekend for me.

Are you ok with pulling the throttle body? Again, it really isn't that hard to do. There are only 2 studs and two bolts holding it in place, but on the side with the studs, you'll also have to take off the nut that attaches a bracket between the cam positioner housing and the throttle body. You'll see what I mean. You'll also have to disconnect the accelerator cable at the bellcrank, this isn't hard to do either.

As far as the coolant hoses go, I think you can get away without draining any radiator fluid first, but I don't remember for sure. My recollection is that as long as you keep the hoses up (don't let them drop), the ends are higher than the top of the radiator. You should check that to be sure.

Once you've got all that out of the way, you just need to disconnect the plug for the ISCM, the TPS plug, and the closed throttle postition switch plug, and you can pull the throttle body off of the intake manifold.

Once you've got it off, you'll see the screws to take out to pull out the ISC motor. There really isn't that much to it. You just need to pull it apart and clean it up with carb cleaner. You'll want to clean up the throttle plate too while you have it all apart.

Mark

Alright, thanks! how long do you think that will take to do? A day? weekend? I dunno, it is very cold here now, so I may just get it done somewhere. I hope that is the answer, you are pretty sure that it is? Well, thanks! Hope your busy weekend went well.

alex

Alex;
Hey, guess what? I was just out checking the oil and other fluids on my car, and I took a look at the throttle plate assy on mine. You can get at the ICS motor without removing the throttle body. Don't try going at this with an el-cheapo phillips screw driver, you need to use a good one. The screws will be in there tight, so make sure you get a good bite on the screw and don't strip the head. You''ll need to remove the aifilter duct hose to get in there. There really isn't much to the ICS motor assembly, you just need to clean it up. I think when you take it apart you'll know right away if you found the problem. I expect you'll find lots of black soot in there. If it looks nice and clean, you probably haven't found the problem, but I doubt you'll find it clean.

Mark

i had my timing belt replaced and then my car started doin the same thing urs is.. idling uneven and slow and stalling off especially with the a/c on.

it turned out that the timing belt wasnt put on right... it was off like 4 teeth or so.. could be ur prob who knows

i'm suprised your car would even run with the timing belt so far off. Most talons have zero tolerance where if the timing is off at all, it could cause serious cylinder or valve damage.

now, if the timing belt was off is it safe to say that it should be doing that idleing thing all the time? because mine only does it some of the time, and when I take of the Idle Sensor Switch it simply revs higher and does not idle unevenly. So, I am doubting the fact that it is the timing belt due to that fact. On a side note: Up here in Alberta it has been MINUS 45 degrees, and my car now ALWAYS does the reving thing, and it seems to be faster between revs now, much faster. So do you think that it is still the ICSM thing?? Let me know!

Thanks!

Alex

Alex;
BRRRRRRRRRR!! You wouldn't catch me working on a car in that weather unless it's in a heated garage!

I do indeed think the problem is between the ICS motor and the closed throttle position switch. From what you described in earier posts, you're getting intermittent continuity on the switch at idle position(you mentioned it testing fine, then coming up with resistance when you checked it again). That in itself can create problems similiar to what you describe, but I'm inclined to believe you aren't getting smooth reaction on the ICS motor as well.

With it being as cold as it is there, I suggest disconnecting the closed throttle position switch for now. It isn't going to hurt anything. You can set your idle up higher for now to compensate for the fact that the ECM isn't controlling it. When the weather gets warmer, I do suggest cleaning out that ICS motor and mechanism, and replacing that closed throttle position switch. You can get the switch at a bone yard for a few dollars.

Mark

Mark

Thanks so much for all your help!! This probably saved my tonnes from a diagnostics test and crap. I will take it out, or take it to someone soon and go from there. I am sure I will call on you again in the near future!!

Take Care!

Alex